Spine stabilization

ABSTRACT

A bone stabilizing plate includes two plate portions, each affixable to bones of a patient, the plate portions telescoping together with mating rails and grooves. A limiter associated with one of the plate portions sliding engages one a catch associated with the other of the plate portions, when the plate portions are telescoped together, and resists stops telescoping when the plate portions are telescoped a predetermined distance apart. Once the limiter and catch are engaged, the plate portions enable imposition of a minimum compressive force between bones connected to the plates. The limiter is resiliently positioned to deflect into a relief formed in its respective plate portion. A groove positioned proximate the catch enables free telescoping motion limited by the engagement of the catch and limiter, whereby the minimum compressive force between bones is maintained, and Wolfe&#39;s Law may apply.

FIELD OF THE INVENTION

The invention relates to bone fixation, and more particularly tofixation of spinal joints using compression imposed by mating plates.

BACKGROUND OF THE INVENTION

Spinal fusion, also known as spondylodesis or spondylosyndesis, is asurgical technique used to join two or more vertebrae. Supplementarybone tissue, from the patient (autograft), a donor (allograft), or froma synthetic material can be used in conjunction with the body's naturalbone growth (osteoblastic) processes to fuse the vertebrae.

Wolfe's Law states that maintaining a compressive load on a graft in aninterbody fusion contributes towards the graft fusing more quickly andor thoroughly.

SUMMARY OF THE INVENTION

An embodiment for stabilizing bones of a patient comprises a first plateportion including at least one aperture for connecting the first plateportion to body tissue of the patient comprises a projection extendingfrom the first plate portion; a second plate portion including at leastone aperture for connecting the second plate portion to body tissue ofthe patient; a chamber formed in the second plate portion sized anddimensioned to slidingly receive the projection, thereby substantiallylimiting movement of the first plate portion relative to the secondplate portion to a telescoping motion when the projection is receivedwithin the chamber; a limiter resiliently extending from one of theprojection or the chamber; a catch formed in the other of the projectionor the chamber, relative to the limiter, operative to form an engagementwith the limiter, the catch further operative to admit passage of thelimiter past the engagement when the first and second plate portions aretelescoped together, the catch further operative to prevent passage ofthe limiter past the engagement of the catch and the limiter when thefirst and second plate portions are telescoped apart.

In further embodiments, the projection forms at least two railsengageable with the chamber; the chamber forms at least two groovesmateable with the at least two rails; a groove formed in the projectionor chamber forming the catch is positioned apart from a location of theengagement when the first and second plate portions are telescopedtogether, the groove operative to admit passage of the limiter between afirst location at a first distance from the engagement and a secondlocation disposed at a distance from the first location; an aperture isformed in the projection or chamber forming the catch, whereby an objectmay be inserted within the aperture to resiliently bend the limiter todisengage the limiter from the catch.

In yet further embodiments, an aperture is formed in the projection orchamber forming the catch, whereby an object may be inserted within theaperture to resiliently bend the limiter to disengage the limiter fromthe groove; and the limiter has a ramped surface and a blocking surface;the catch further includes a blocking surface, the blocking surface ofthe limiter mateably engageable with the blocking surface of the catchto prevent telescoping apart of the first plate portion and the secondplate portion.

In another embodiment, the bones of the patient are jointed bones, andthe first plate portion is engageable with bones of a first side of thejoint, and the second plate portion is engageable with bones on asecond, opposite side of the joint; when the first plate portion and thesecond plate portion are telescoped together, a compressive force isapplied to the jointed bones; the compressive force is operative topromote a fusion of bones of the patient; the limiter forms a curvedprofile mateable with a curved profile of the catch; the chamber furtherincludes a viewing aperture positioned formed in the chamber andoperative to enable viewing of an extent of telescoping of the firstplate portion with the second plate portion; and the viewing apertureincludes formations enabling a quantification of an extent oftelescoping of the first and second plate portions.

In yet another embodiment, a device for applying a compressive force toseparated bones of a patient, comprises a first plate portion includingat least one aperture for connecting the first plate portion to a firstbone of the patient; a projection extending from the first plateportion; a second plate portion including at least one aperture forconnecting the second plate portion to a second bone of the patient, thesecond bone separated from the first bone by a bone graft; a chamberformed in the second plate portion sized and dimensioned to slidinglyreceive the projection, thereby substantially limiting movement of thefirst plate portion relative to the second plate portion to atelescoping motion when the projection is received within the chamber; acatch formed in one of the projection or the chamber, operative to forman engagement with the limiter, the catch further operative to admitpassage of the limiter past the engagement when the first and secondplate portions are telescoped together, the catch further operative toprevent passage of the limiter past the engagement of the catch and thelimiter when the first and second plate portions are telescoped apart; alimiter resiliently extending from the other of the projection or thechamber relative to the catch, and having a surface angled to slidinglyengage the catch, and an opposing surface angled to resist movement whenengaged with the catch; and a groove is formed in the projection orchamber forming the catch, the groove positioned apart from a locationof the engagement when the first and second plate portions aretelescoped together, the groove operative to admit passage of thelimiter between a first location at a first distance from the engagementand a second location disposed at a substantial distance from the firstlocation.

In another embodiment, a device for applying a compressive force toseparated bones of a patient comprises a first plate portion includingat least one aperture for connecting the first plate portion to a firstbone of the patient; a projection extending from the first plateportion; a second plate portion including at least one aperture forconnecting the second plate portion to a second bone of the patient, thesecond bone separated from the first bone by a bone graft; a chamberformed in the second plate portion sized and dimensioned to slidinglyreceive the projection, thereby substantially limiting movement of thefirst plate portion relative to the second plate portion to atelescoping motion when the projection is received within the chamber; acatch formed in one of the projection or the chamber, operative to forman engagement with the limiter, the catch further operative to admitpassage of the limiter past the engagement when the first and secondplate portions are telescoped together, the catch further operative toprevent passage of the limiter past the engagement of the catch and thelimiter when the first and second plate portions are telescoped apart; alimiter resiliently extending from the other of the projection or thechamber relative to the catch, and having a surface angled to slidinglyengage the catch, and an opposing surface angled to resist movement whenengaged with the catch; and a viewing aperture positioned in the chamberand operative to enable viewing of an extent of telescoping of the firstplate portion with the second plate portion.

In a yet further embodiment, the limiter includes a relief formed in theprojection or chamber from which the limiter extends, the limiteroperative to resiliently bend and deflect into the relief.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention, and theattendant advantages and features thereof, will be more readilyunderstood by reference to the following detailed description whenconsidered in conjunction with the accompanying drawings wherein:

FIGS. 1 and 2 depict perspective views of a first embodiment of mateablestabilization plates;

FIGS. 3 through 14 depict various views of a second embodiment ofmateable stabilization plates;

FIGS. 15-22 depict various views of a third embodiment of mateablestabilization plates, including limiters;

FIGS. 23-25 depict the embodiment of FIGS. 15-22, in three differentstates of compression;

FIGS. 26-29 depict alternative views of the embodiment of FIGS. 15-25;

FIGS. 30-42 depict various views of a fourth embodiment of mateablestabilization plates;

FIGS. 43-57 depict various views of a fifth embodiment of mateablestabilization plates, including a resilient and separable limiter; and

FIGS. 58-60 depict alternative examples of implantation of embodimentsof mateable stabilization plates.

DETAILED DESCRIPTION OF THE INVENTION

In the description which follows, any reference to direction ororientation is intended primarily and solely for purposes ofillustration and is not intended in any way as a limitation to the scopeof the present invention. Also, the particular embodiments describedherein are not to be considered as limiting of the present invention.

Referring now to the figures, in which like reference numerals refer tolike elements, FIGS. 1-2 illustrate a bone stabilization device 100including a receiver 200 and an insert 300. A chamber 202 open at an end204 of section 200 is sized and dimensioned to slidably receive andretain a projection 302 disposed at an end 304 of insert 300. Receiver200 and insert 300 are provided with one or more fastener apertures 206,306, respectively, operative to facilitate connection of receiver 200and insert 300 to bones or other tissue of a patient.

With reference to FIGS. 58-60, it may be seen that device 100 isimplantable within the body, in connection with vertebrae 502, 504, 506of the spine 500. The vertebrae shown are exemplary, and devicesdisclosed herein may be used with any vertebrae of the spine. Device 100may be connected to an anterior, posterior, medial, or lateral aspect ofthe spine, using any acceptable approach, or any known method, includingopen or minimally invasive. Device 100 may further be connectedanteriorly, posteriorly, or laterally, to non-adjacent vertebrae, as maybe seen for example in FIG. 59. While device 100 is advantageously usedto stabilize vertebrae, other bones of the body may be stabilized usingdevice 100, including other joints, or to stabilize non-jointed portionsof bones, for example bones that have been fractured.

With further reference to FIGS. 1-2, locking elements 208, 308 may beprovided, operative to ensure fasteners inserted within apertures 206,306 do not reverse from engagement with the body.

Additional apertures 210, 212, 310, 312 may be provided to operativelyserve at least one of the following: engaging fasteners, provide anobservation window to underlying areas, provide an access port tounderlying tissue, provide an area to pack bone graft or other bonegrowth stimulating materials and/or releasably connect device 100 withsurgical or manipulative instrumentation. Elongated aperture 314,visible in FIG. 2, slideably receives a fastener 316 which is passedthrough an opening 216 in chamber 202. Locking means 218 may be providedto ensure fastener 316 remains in secure engagement with device 100,including, for example, knurling, a locking washer, a cover, or a lockengageable with a portion of fastener 316, such as is shown, forexample, as lock 208. Insert 300 may further be secured relative toreceiver 200 at any point along the length of aperture 314 in which post320 may reside, whereby a continuous range of adjustment is possible.

It may be desired to allow receiver 200 and insert 300 to remain inmutual slideable engagement within the body. Therapeutic benefits wouldinclude restricting ranges of motion, for example flexion or extension,while enabling compression and distraction. In this application, it maybe advantageous for fastener 316 to securely engage a portion 202, as bythreading, compression, adhesion, or welding, whereby a post portion 320of fastener 316 may freely slide within aperture 314 of insert 300.Alternatively, not shown, chamber 202 may be provided with an elongatedaperture as shown for aperture 314, and a post 320 may be associatedwith insert 302.

In another application, it may be advantageous to fasten receiver 200and or insert 300 to the body, therapeutically adjust a disposition ofbones of the body, and then securely fasten receiver 200 and insert 300in a fixed relative configuration. In this application, it may beadvantageous to connect receiver 200 and insert 300 in slideablealignment, and expeditiously tighten receiver 200 and insert 200together once a desired position has been attained. Accordingly,connector 220 may releasably engage fastener 316, for example bythreaded attachment 222, whereby when post 320 passes through opening216, through aperture 314, and into engagement with connector 220,receiver 200 and insert 300 may slide relative to each other, but notseparate. When a disposition of bones has been achieved, fastener 316may be securely fastened to connector 220, whereupon projection 302 ispinched against one or more surfaces of chamber 202, and may no longerslide relative to chamber 202. To promote a secure connection betweenprojection 302 and chamber 202, a surface 224 of connector 220 may beprovided with a knurled or roughened surface, as may a complementarycontacting surface 324 of projection 302 and or chamber 202. Foradditional strength or reliability, a plurality of fasteners 316 and orconnectors 220 may be used. A single fastener has an advantage of quickinstallation and adjustment, decreasing the duration of surgery.

Receiver 200 and insert 300 may advantageously be assembled andsterilized prior to surgery, together with fastener 316 and connector220, for example as part of a manufacturing and quality control process,thereby facilitating surgical preparation by eliminating interoperativeassembly, and reducing the complexity and duration of surgery, whilereducing the probability of assembly error.

In yet another application, receiver 200 and insert 300 are mutuallyconnected, and engaged to respective portions of body tissue.Subsequently, receiver 200 and insert 300 are each engaged by aninstrument, not shown, for example through connection with one or moreof aperture 310 of insert 300, and aperture 210, 212, or narrowedportion 226, of receiver 200. In this manner, receiver 200 and insert300 may be compressed together, or expanded apart, thereby producing acommensurate change in the relative alignment of attached tissue,whereupon fastener 316 may then be tightened to maintain a desiredalignment. A slot 230 may be provided, formed in a portion of chamber202, operative to admit passage of a portion of fastener 316, to permitpassage of body fluids or tissue ingrowth into chamber 202, to reduceweight of device 100, and or to facilitate attachment of connector 220.

Receiver 200 and insert 300 interconnect in sliding mutual engagementalong a predetermined pathway which may be straight or curved, definedby mating rails 332 and grooves 232, each of rail 332 guided along apathway defined by a respective groove 232. In this manner, telescopingmovement of receiver 200 and insert 300 may be defined to a single planeor curved pathway, thereby enabling compression or distraction, whilestabilizing along other axes. The mating rail 332 and groove 232 enablea bending or twisting load to be distributed across the length of mutualengagement of rails 332 and grooves 232, providing increased strength,reducing the incidence and severity of potential stress raisers, andpreventing disengagement along an anterior-posterior direction whendevice 100 is implanted in the spine.

Receiver 200 and insert 300 are each provided with a narrowed portion226, 326, respectively, advantageously sized to facilitate insertion ofdevice 100 into the body through a percutaneous puncture or minimalincision, to provide good visualization of underlying tissues, and or toreduce impact upon surrounding tissues at the site of implantation.Further, head portions 228, 328 may be angled, and or provided withcurved surfaces, to better conform to intended attachment surfaces inthe body. As such, device 100 may be provided in left or rightconfigurations, and may be provided in a range of sizes orconfigurations appropriate for the size, gender, or age of the patient.For each size, device 100 enables a low profile, or reduced dimensionalsize, thereby reducing dislocation of body tissue, facilitatingimplantation, and increasing patient comfort.

As a sliding or telescoping engagement is formed between receiver 200and insert 300 at a location disposed away from bone engaging headportions 228, 328, greater flexibility in an orientation and shape ofhead portions 228, 328 is possible. In particular, portions of device100 that interface with the spine may be contoured to match the naturalanatomy of the vertebral bodies, without a requirement of slots oradjustments at these interface regions. Accordingly, an optimalconfiguration, for example, of apertures 206, 306 and associated lockingmechanisms 208, 308, is achieved.

Device 100 may be used, for example, in the case of a trauma, tumor ordeformity in the human spine where one or more vertebral bodies arecompromised. In certain instances, it is advantageous to perform acorpectomy where the damaged portions of the vertebrae are removed. Acage or bone graft is inserted into the resulting space to replace theremoved tissue. In addition to the cage or graft, device 100 is providedoperative to span the now weakened area, and provide stabilization whiletissues reform and native strength is restored, or as a longer termsource of stabilization.

In an application, a compressive force is applied by device 100 to abone graft or other implanted material, and or bones or other tissue ofthe patient, whereby Wolfe's Law may apply. After an initialimplantation, an increase or decrease in compressive force may beachieved by loosening fastener 316, changing a disposition of bodytissue, and refastening 316, for example through a minimally invasiveprocedure. Such increase in compressive force may advantageouslycompensate, for example, for graft subsidence.

Referring now to FIGS. 3-12, an alternative device 100A includes grooves232 and rails 332 which mutually form a tongue and groove connection. Inthis embodiment, receiver 200 and insert 300 are provided with a curvedprofile indicated by arrow “A”, which is operative to conform to curvedanatomy at an implant location, and or to provide additional bendingstiffness for device 100A, for example to reduce a likelihood of bendingin a direction transverse to curve “A”, corresponding to flexion andextension of the spine. In another embodiment, receiver 200 and insert300 may also be provided with a curved profile extending in a transversedirection from arrow “A.” In addition, grooves 232 and rails 332 areangled with respect to the coronal plane of the spine, providingadditional resistance to bending of device 100 when implanted in an APorientation. Further, by disposing rails 332 at an angle, an increasedquantity of material may be used to form rails 332, manifested in anenlarged cross-section of the jointed surfaces, thereby increasing thestrength of the mated receiver 200 and insert 300. Further, the angleddisposition exhibits a tendency for self-centering, and is thereby lessprone to a toggling or side to side movement, thereby transmitting loadmore evenly throughout the mated rail 332 and guide 232 surfaces,resulting in an increased strength and durability. More particularly, aposition of lowest potential energy exists in which rails 332 andgrooves 232 are lying at the same angle with respect to each other, dueto their mutually ramped angular disposition relative to a direction ofsliding engagement.

Device 100A is illustrated in FIGS. 13-14, with rails 332 insertedwithin grooves 232, with FIG. 14 illustrating a complete extent ofcompression. With reference to overlapping apertures 212, 312, a visibleindication of an extent of compression may be seen, by directobservation in the assembly or operating theatre, and with imaging,which may be facilitated if device 100A is formed with radiopaquematerial at least in this area.

Devices of the various embodiments disclosed herein enable a reductionor elimination of movement of a stabilizing plate relative to a bonescrew or anchor head, thereby reducing disease caused by an implantelement rubbing or contacting body tissue, including an adjacent disc.

With reference to FIGS. 15-29, an alternative embodiment, device 100B,is illustrated, which forms a hybrid stabilizer having a dynamic rangeof compression following an initial amount of static compression. Device100B includes one or more limiters 534 engageable with one or morecatches 634. Limiter 534 includes a projecting surface 536 resilientlyconnected to receiver 200. In the embodiment of FIGS. 15-29, extension238 resiliently depends from receiver 200, and projecting surface 536 isdisposed about an end of extension 238.

Where two or more limiters 534 are used, it is advantageous to ensureall limiters are engaged to their respective catches 634 at the sametime. With appropriate design and manufacturing tolerances, the slidingcoordination of rails 332 and grooves 232 reduces side to side, jamming,or toggling motions of receiver 200 and insert 300, which couldotherwise enable an uneven engagement.

Projecting surface 536 is advantageously formed with a steeply angledsurface 550 extending in a direction away from head portion 228, and aramped surface extending in direction towards head portion 228. In thismanner, when receiver 200 and insert 300 are assembled together,projecting surface may be deflected by catch 634 to resiliently bendextension 238 to admit passage of limiter 534 past catch 634. Similarly,the steeply angled surface of projecting surface 536 is thereafterconstrained against a mating surface of catch 634 whereby extension 238is not caused to bend, and maintenance of a mutual engagement ofreceiver 200 and insert 300 is thus fostered. A force required to bendextension 238 may be targeted to result in resistance to engagement oflimiter 534 and catch 634 until a sufficient compressive force isapplied to the receiver 200 and insert 300. In this manner, a deviceimplanted with an unengaged limiter 534 may become engaged when asufficient range of motion has been achieved, for example duringtherapeutic exercise, or after a predetermined extent of graftsubsidence or tissue healing has occurred.

A groove or channel 240 may be seen in FIG. 16, having a purpose bestunderstood with further reference to FIGS. 19-20, and 27-29, inparticular. An opening 340 is provided in insert 300, operative to admitpassage of a pin 342 through end 304 and into channel 240, when insert300 is assembled into receiver 200. Access to end 304 of insert 300, forinsertion of pin 342 after assembly, is provided through slot 230 ofreceiver 200. When pin 342 is disposed through insert 300 and withinchannel 240, movement of receiver 200 and insert 300 relative to eachother is constrained to an extent of travel of pin 342 within channel240. As such, receiver 200 and insert 300 are further maintained in aninterconnected state by pin 342. It may be advantageous to preassemblereceiver 200 and insert 300 as part of a manufacturing process, or priorto surgery. In this manner, for example, pin 342 is assembled into end304 and channel 240; however, receiver 200 and insert 300 areadvantageously not sufficiently collapsed together to a point wherelimiter 534 is engaged past catch 634.

In the operating theatre, receiver 200 is engaged with body tissue, forexample a first vertebra, and insert 300, preassembled into receiver 200and optionally retained therein by pin 342, is engaged with a differentportion of body tissue, for example a second vertebra. Engagement ofreceiver 200 and insert 300 is by any known means, including screws,polyaxial screws, pedicle screws, bone screws, staples, clips, anchors,adhesive, suture, and or wire. Advantageously, graft material is placedinto the body prior to engagement of device 100B.

Once receiver 200 and insert 300 are engaged with the body, tissue andor graft material positioned between engaged body portions may becompressed towards each other. In one embodiment, the body tissue iscompressed using any known means, including directly engaging the bodytissue. In another embodiment, receiver 200 and insert 300 are directlymanipulated and moved closer together into further mutual slidingengagement, and through their respective connections with body tissue,cause the body tissue portions to move or to be compressed together. Tofacilitate this action, one or more engagement formations 244 inreceiver 200, and or engagement formations 344 in insert 300, areoperative to enable secure engagement with a compression instrument, notshown. Such compression instrument may be of a prior art design, forwhich device 100B is adapted, or an instrument may be adapted or createdfor engagement with specific engagement formations 244, 344 of device100A. Engagement formations 244, 344 may have the form, for example, ofdepressions, projections, or apertures, and may be threaded or otherwiseconfigured for secure engagement with a hand, and or an instrument ortool.

It is contemplated that an initial amount of compression engages limiter534 and catch 634, whereby the body tissue portions may furthercompress, however a minimum amount of compression is continuouslymaintained, advantageously sufficient to exploit Wolfe's Law. Limitergrooves 646 may be provided to protect and guide limiters 534 duringrelative movement of receiver 200 and insert 300.

Aperture 212 is provided with indicating formations 246, spaced atregular intervals, for example 1 mm, although other intervals mayadvantageously be employed. Indicating formations may have the shape ofa projection extending into aperture 212, or may be formed as one ormore angled lines, as may be seen in FIGS. 13-14. Through directobservation through aperture 212, inter-operatively and or throughimaging, an alignment of a surface of insert 300 with respect toindicating formations 246 serves to indicate an extent of compression ofreceiver 200 relative to insert 300. Knowledge of an extent ofcompression may be used to understand a current disposition of bodytissue, and to plan and measure a therapeutic change in compression.

Referring now to FIGS. 23-25, the aforedescribed levels of compressionof device 100B may be seen. In FIG. 23, limiters 534 have not engaged,or passed beyond, catches 634, and no portion of insert 300 is visiblewithin aperture 212, indicating a current state of assembly. Althoughnot required, pin 342 has advantageously been engaged within channel240. In FIG. 24, limiters 534 have passed beyond catches 634, and ifdevice 100B were implanted, a minimum amount of compression would beachieved. End 304 of insert 300 is now visible within aperture 212. Inparticular, a line demarcating end 304 may be compared with indicatingformations 246. For example, indicating formations 246 may be positioned1 mm apart, or any other distance apart which may be meaningful for aparticular therapeutic application. It may be seen that if a distancebetween indicating formations 246 is known, an extent of compression maybe determined. In FIG. 25, receiver 200 and insert 300 are fullycompressed; however, it should be noted that movement apart of receiver200 and insert 300 is possible.

It may be advantageous to impose an initial amount of compression notonly to encourage tissue growth, ingrowth, or fusion. An objective of amedical practitioner may be to insert an amount of graft or implantmaterial sufficient to cause a desired amount of compression betweenbody tissue and the implanted material, whereby surrounding body tissue,for example ligamentous tissue, provides the compressive force. However,if excess tissue is removed, or surrounding tissue does not createsufficient compression, the initial force imposed by engaging limiter534 and catch 634 may provide the requisite compression. In addition,further compression may be imposed during flexion and extension of thejoint. For example, receiver 200 and insert 300 may freely move furthertogether due to natural kinematics of the joint.

While limiter 534 is shown and described as connected to receiver 200,it should be understood that catch 634 may be connected to receiver 200,and limiter 534 may be connected to insert 300. It is further noted thatrails 332 and mating grooves 232 of device 100B are shaped with adifferent angle than corresponding rails 332 and grooves 232 of device100A, although it should be understood that rails 332 and grooves 232 ofdevice 100B may have the same or similar angle to that of device 100A.

Similarly, other features and corresponding advantages of the variousembodiments herein may be interchanged or combined, as would beunderstood by one skilled in the art. More particularly, each embodimentof device 100 illustrates a particular combination of features, and forclarity, not all features or combination of features are illustrated foreach device.

With reference to FIGS. 30-37, device 100C illustrates an alternativeembodiment having a single limiter 534 and single catch 634. As withdevice 100B, extension 238 is dimensioned and configured to flex andadmit passage of projecting surface 536 over catch 634 when insert 300is urged towards receiver 200 with a predetermined minimum force. In oneembodiment, this minimum force corresponds to correct implantation bythe medical practitioner, whereupon engagement of projecting surface 536and catch 634 will introduce a proper compressive force to promoteWolfe's Law. In another embodiment, this minimum force corresponds to apostoperative range of motion indicating that a minimum compressiveforce should be established and thereafter maintained.

Devices of the disclosure advantageously adjust for changes in graftheight, postoperatively, as needed. In this manner, load may bemaintained on graft of an interbody fusion to ensure that the graft isfused thoroughly and as quickly as possible, in accordance with Wolfe'sLaw. For cervical plating, in particular, a semi-rigid fixation may beadvantageous. Devices of the disclosure accommodate this requirement byenabling a height adjustment postoperatively. This adjustability isprovided by segments, or insert 300 and receiver 200, that telescope, orcollapse and or expand in mutual connection, to a therapeuticallyeffective height, thereby ensuring graft contact with the vertebral bodyendplates. By combining this dynamic aspect with a limiter 534, theamount of unloading of the graft may be limited, while preserving adynamic height adjustment. Limiter 534 thus has at least two functions:helping to maintain receiver 200 and insert 300 in telescopingengagement, and providing a minimum amount of compression.

Reference may now be had to FIGS. 43-57, illustrating device 100D. InFIGS. 43-46 in particular, receiver 200 is illustrated in which limiter534 is positioned to extend from insert 300, and catch 634 and limitergroove 646 are positioned within receiver 200. An additional catch 634Ais positioned to engage limiter 534 prior to engagement of limiter 534with catch 634, as explained further below.

In FIGS. 47-49, insert 300 includes a chamber or spring relief 538positioned within end 304, illustrated in cross section in FIG. 49.Notched steps 540 are formed at opposite ends of relief 538. A relieffloor 542 is positioned at a greater depth within relief 538 than steps540. With reference to FIGS. 50-52, a limiter 534A includes a projectingsurface 536A. Limiter 534A is illustrated as a separate element relativeto insert 300, although it should be understood that limiter 534A may beconnected to insert 300, for example with a living hinge (not shown) atan end 544 of insert 300. However, it may be simpler, for example, tomanufacturing limiter 534A separated, as shown. Opposing ends 544 oflimiter 534A rest upon steps 540 of relief 538, whereby limiter 534A mayresiliently bend downwards in a direction indicated by arrow “A”. Hinge546 is formed as a notch between projecting surfaces 536A, enablingprojecting surfaces 536A to move closer together during bending oflimiter 534A at hinge 546.

A curved profile, indicated by arrow “B”, is formed by upper surfaces548 of projections 536A. This curved profile corresponds to that of arch648 of receiver 200, shown in FIG. 46. As insert 300 is moved intoreceiver 200, upper surfaces 548 mate with arch 648, together uniformlydistributing a load or force of deflection to smoothly and reliablyguide projections 536A downwards, thereby deflecting limiter 534A athinge 546, in the direction of arrow “A”. Relief 538 is sized anddimensioned so that limiter 534A may only resiliently deflect towardsrelief floor 542, and limiter 534A is prevented from movement in otherdirections.

As insert 300 of device 100D is passed into receiver 300, engaging rails332 and grooves 232, an initial catch 634A mates with projectingsurfaces 536A, after which insert 300 and receiver are retained inmutual engagement by an engagement of steeply angled surface 550 and amating surface of initial catch 634A. Engagement at this level may beused, for example, to maintain insert 300 and receiver 200 in mutualengagement, or to impose a minimum level of compression of body tissueas described elsewhere herein. Insert 300 may be urged further withinreceiver 200, as by use of a compression tool during surgery, or throughcarrying out sufficient range of motion of body tissue connected todevice 100D. Movement of insert 300 further into receiver 200 causesprojecting surfaces 634A to deflect limiter 534A, bending hinge 546,through interaction of ramped surface 552 (FIG. 51) of projectingsurfaces 536A against arch 648. After insert 300 has moved a sufficientdistance, projecting surfaces 536A abut limiter groove 646, allowinglimiter 534A to resiliently resume an unbent configuration, whereinlimiter 534A now limits movement of insert 300 to an extent of a lengthof limiter groove 646. As with initial catch 634A, limiter groove 646forms a mating surface with steeply angled surface 550, whereby insert300 is maintained within receiver 200. To disengage limiter 634A fromengagement within limiter groove 646, an object, such as a tool, may beinserted within opening 248, to deflect limiter 634A and clear steeplyprojecting surface s 636A from engagement within limiter groove 646. Asimilar opening, not shown, may be provided to enable disengagement frominitial catch 634A.

In one embodiment, by first engaging initial catch 634A, an initial orminimum compression is applied to a bone graft. This minimum compressionis maintained, while a dynamic range of motion imposing at least thisminimum compression may subsequently be enabled by device 100D, whenlimiter groove 646 is engaged. Subsequent to enabling the dynamic rangeof motion, an excess unloading of the graft is ensured throughengagement at a limit of limiter groove 646. In this manner, levels oftensile or extension movement are established which foster healing inaccordance with Wolfe's Law.

It will be appreciated by persons skilled in the art that the presentinvention is not limited to what has been particularly shown anddescribed herein above. In addition, unless mention was made above tothe contrary, it should be noted that all of the accompanying drawingsare not to scale. A variety of modifications and variations are possiblein light of the above teachings without departing from the scope andspirit of the invention.

All references cited herein are expressly incorporated by reference intheir entirety. In addition, unless mention was made above to thecontrary, it should be noted that all of the accompanying drawings arenot to scale. There are many different features to the present inventionand it is contemplated that these features may be used together orseparately. Thus, the invention should not be limited to any particularcombination of features or to a particular application of the invention.Further, it should be understood that variations and modificationswithin the spirit and scope of the invention might occur to thoseskilled in the art to which the invention pertains. Accordingly, allexpedient modifications readily attainable by one versed in the art fromthe disclosure set forth herein that are within the scope and spirit ofthe present invention are to be included as further embodiments of thepresent invention.

What is claimed is:
 1. A device for stabilizing bones of a patient,comprising: a first plate portion having an upper surface configured toface away from body tissue of a patient and a lower surface configuredto face said body tissue of said patient including at least one aperturefor receiving a first element to connect said first plate portion tosaid body tissue of said patient; a projection extending from said firstplate portion; a second plate portion including at least one aperturefor receiving a second element to connect said second plate portion tosaid body tissue of said patient; a chamber formed in said second plateportion sized and dimensioned to receive said projection, therebysubstantially limiting movement of said first plate portion relative tosaid second plate portion to a motion in a first direction and in anopposite second direction when said projection is received within saidchamber; a limiter resiliently extending from one of said projection orsaid chamber, wherein said limiter is bendable such that said limiter ismovable away from said upper surface of said first plate portion towardsaid lower surface of said first plate portion; a catch formed in saidother of said projection or said chamber, relative to said limiter,operative to form an engagement with said limiter, said catch furtheroperative to admit passage of said limiter past said engagement whensaid first and second plate portions are moved in said first direction,said catch further operative to prevent passage of said limiter pastsaid engagement of said catch and said limiter when said first andsecond plate portions are moved in said second direction wherein saidprojection includes a spring relief formed therein, the spring reliefreceiving the limiter, the spring relief having notched steps formed atopposite ends of said spring relief and a relief floor positioned at adepth greater within said spring relief than said notched steps therebyallowing the limiter to rest upon the notched steps while the limiter isengaged with the notched steps and permit the limiter to resilientlybend downwards towards the relief floor during use such that the limiterreleases from the notched steps when the limiter bends downwards towardsthe relief floor.
 2. The device of claim 1, wherein said projectionforms at least two rails engageable with said chamber.
 3. The device ofclaim 2, wherein said chamber forms at least two grooves mateable withsaid at least two rails.
 4. The device of claim 1, further including agroove formed in said projection or chamber forming said catch, saidgroove positioned apart from a location of said engagement when saidfirst and second plate portions are moved in said first direction, saidgroove operative to admit passage of said limiter between a firstlocation at a first distance from said engagement and a second locationdisposed at a substantial distance from said first location.
 5. Thedevice of claim 1, further including an aperture formed in saidprojection or chamber forming said catch, whereby an object may beinserted within said aperture to resiliently bend said limiter todisengage said limiter from said catch.
 6. The device of claim 4,further including an aperture formed in said projection or chamberforming said catch, whereby an object may be inserted within saidaperture to resiliently bend said limiter to disengage said limiter fromsaid groove.
 7. The device of claim 1, wherein said limiter has a rampedsurface and a blocking surface.
 8. The device of claim 7, said catchfurther including a blocking surface, said blocking surface of saidlimiter mateably engageable with said blocking surface of said catch toprevent movement in said second direction of said first plate portionand said second plate portion.
 9. The device of claim 1, wherein saidlimiter forms a curved profile mateable with a curved profile of saidcatch.
 10. The device of claim 1, wherein said chamber further includesa viewing aperture formed in said chamber and operative to enableviewing of an extent of telescoping of said first plate portion withsaid second plate portion.
 11. The device of claim 1, wherein said catchcomprises a limiter groove having a length operative to impose at leasta minimum compression and a dynamic range of motion.
 12. The device ofclaim 1, further comprising an initial catch formed in said other ofsaid projection or said chamber, relative to said limiter, and operativeto apply an initial or minimum compression.
 13. The device of claim 1,wherein said projection has a superior surface and opposing lateralsides, wherein said opposing lateral sides include opposing lateralrails, said chamber forms an upper surface and opposing groovesconfigured to mate with and engage said opposing lateral rails of saidprojection, said limiter extends from one of said superior surface ofsaid projection or said upper surface of said chamber, and said catch isformed in said other of said superior surface of said projection or saidupper surface of said chamber.
 14. A device for applying a compressiveforce to separated bones of a patient, comprising: a first plate portionhaving an upper surface configured to face away from a first bone of apatient and a lower surface configured to face said first bone of saidpatient including at least one aperture for receiving a first element toconnect said first plate portion to said first bone of said patient; aprojection extending from said first plate portion; a second plateportion including at least one aperture for receiving a second elementto connect said second plate portion to a second bone of said patient,said second bone separated from said first bone by a bone graft; achamber formed in said second plate portion sized and dimensioned toreceive said projection, thereby substantially limiting movement of saidfirst plate portion relative to said second plate portion to a motion ina first direction and an opposite second direction when said projectionis received within said chamber, wherein said chamber further comprisesnotched steps and a relief floor positioned at a greater depth than saidsteps; a catch formed in one of said projection or said chamber,operative to form an engagement with a limiter, said catch furtheroperative to admit passage of a said limiter past said engagement whensaid first and second plate portions are moved in said first direction,said catch further operative to prevent passage of a said limiter pastsaid engagement of said catch and said limiter when said first andsecond plate portions are moved in said second direction; and whereinsaid limiter resiliently extending from said other of said projection orsaid chamber relative to said catch, and having a surface angled toslidingly engage said catch, and an opposing surface angled to resistmovement when engaged with said catch, wherein said limiter is bendablesuch that said limiter is movable away from said upper surface of saidfirst plate portion toward said lower surface of the first plateportion, wherein said projection includes a spring relief formedtherein, the spring relief receiving the limiter, the spring reliefhaving notched steps formed at opposite ends of said spring relief and arelief floor positioned at a depth greater within said spring reliefthan said notched steps thereby allowing the limiter to rest upon thenotched steps while the limiter is engaged with the notched steps andpermit the limiter to resiliently bend downwards towards the relieffloor during use such that the limiter releases from the notched stepswhen the limiter bends downwards towards the relief floor.
 15. Thedevice of claim 14, wherein said projection forms at least two railsengageable with said chamber.
 16. The device of claim 15, wherein saidchamber forms at least two grooves mateable with said at least tworails.
 17. The device of claim 14, further including a groove formed insaid projection or chamber forming said catch, said groove positionedapart from a location of said engagement when said first and secondplate portions are moved in said first direction, said groove operativeto admit passage of said limiter between a first location at a firstdistance from said engagement and a second location disposed at asubstantial distance from said first location.
 18. A device for applyinga compressive force to separated bones of a patient, comprising: a firstplate portion having an upper surface configured to face away from afirst bone of a patient and a lower surface configured to face saidfirst bone of said patient including at least one aperture for receivingan element to connect said first plate portion to said first bone ofsaid patient; a projection extending from said first plate portion; asecond plate portion including at least one aperture for connecting saidsecond plate portion to a second bone of said patient, said second boneseparated from said first bone by a bone graft; a chamber formed in saidsecond plate portion sized and dimensioned to slidingly receive saidprojection, thereby substantially limiting movement of said first plateportion relative to said second plate portion to a motion in a firstdirection and an opposite second direction when said projection isreceived within said chamber; a first catch formed in one of saidprojection or said chamber, operative to form an engagement with alimiter, said catch further operative to admit passage of said limiterpast said engagement when said first and second plate portions are movedin said first direction, said catch further operative to prevent passageof said limiter past said engagement of said catch and said limiter whensaid first and second plate portions are moved in said second direction;wherein said limiter resiliently extending from said other of saidprojection or said chamber relative to said first catch, and having asurface angled to slidingly engage said first catch, and an opposingsurface angled to resist movement when engaged with said first catch,wherein said limiter is bendable such that said limiter is movable awayfrom said upper surface of said first plate portion toward said lowersurface of the first plate portion; and a viewing aperture positioned insaid chamber and operative to enable viewing of an extent of telescopingof said first plate portion with said second plate portion wherein saidprojection includes a spring relief formed therein, the spring reliefreceiving the limiter, the spring relief having notched steps formed atopposite ends of said spring relief and a relief floor positioned at adepth greater within said spring relief than said notched steps therebyallowing the limiter to rest upon the notched steps while the limiter isengaged with the notched steps and permit the limiter to resilientlybend downwards towards the relief floor during use such that the limiterreleases from the notched steps when the limiter bends downwards towardsthe relief floor.
 19. The device of claim 18, wherein said limiterincludes a relief formed in said projection or chamber from which saidlimiter extends, said limiter operative to resiliently bend and deflectinto said relief.